Digital storage systems are utilized to store digital assets such as video, audio, executable and non-executable computer programs, and data files. These systems generally utilize magnetic or optical media. Some systems, primarily of the magnetic type, are capable of a multiplicity of read/write cycles, while other systems primarily of the optical type, are capable of greater data storage densities but are usually limited to a single write cycle with a multiplicity of read cycles.
Although entities producing digital assets on optically readable discs may do so in a variety of formats, end users commonly have the equipment to read only a subset of the group of available formats. Because each format has an inherent set of available features which may lend the format to a particular type of digital asset, producers must limit themselves to the production of discs (and therefore the content features) having that combination of features required by the content which is most readily readable by the intended end user.
Digital assets are commonly written to 12.0 cm optical discs in one of the following formats:
CD-DA (Compact Disc-Digital Audio) PA1 CD-ROM (Compact Disc-Read Only Memory) PA1 CD-R (Compact Disc-Recordable) PA1 CD-RW (Compact Disc-ReWritable) PA1 "Mixed Mode" CD PA1 Hidden Track (a.k.a. I-Track, ROM Ready, and AUDIOVISION.TM.) PA1 Enhanced Audio Product (a.k.a. SELECTWARE.TM.) PA1 CD+ (a.k.a. Stamped Multisession, and CD Extra) PA1 CD-I Ready (Compact Disc-Interactive) PA1 CD+G (Compact Disc+Graphics) PA1 PHOTO CD PA1 KARAOKE CD PA1 DVD-ROM (Digital Versatile Disc-Read Only Memory) PA1 DVD-Audio (Digital Versatile Disc-Audio) PA1 DVD-Video (Digital Versatile Disc-Video) PA1 DVD-RAM (Digital Versatile Disc-Random Access Memory) PA1 DVD-R (Digital Versatile Disc-Recordable) PA1 Divx-DVD
There are of course other formats and reader/writers capable of reading and/or writing in multiple formats. For example, certain DVD players are capable of reading CD-ROM discs in various formats and certain CD drives are capable of reading CD-DA, CD-ROM, CD-RW, CD-R, PHOTO CD, KARAOKE CD, ISO 9660, and HFS Discs.
There are also known to the art standards for recording various formats on a single sided optical disc. For example, the UNIVERSAL DISK FORMA.TM. (see Universal Disk Format Specification, Optical Storage Technology Association OSTA-2 Revision 1.50, Feb. 4, 1997) and Mixed-Mode CD ROM (see Integrating Mixed-Mode CD-ROM, CINRAM, J. Busk, Feb. 6, 1992).
Likewise, there are several methods known of recording optical media. For example, Horimai, U.S. Pat. No. 5,623,478 teaches recording a first and second pit string on opposite sides of a track center. Additionally, Slaten, U.S. Pat. No. 4,310,919 teaches a two sided video disc member wherein both sides contain digital information. Further, Hinz, U.S. Pat. No. 5,540,966 teaches a dual layer optical medium utilizing at least one partially reflective layer such that both layers may be read from a single optical storage disc side.
Thus the prior art teaches multi-layer optical discs, dual sided optical discs, multiple data formats, and readers capable of reading multiple formats. However, the prior art does not teach a dual sided optical disc having different formats on opposing sides.